1. Field of the Invention
This present invention pertains to pile drivers, and more particularly to a ramming apparatus, a system incorporating the ramming apparatus and methods and applications for driving objects into soil under deep water.
2. Description of the Related Art
Large, heavy, surface-powered hammering devices exist for the purpose of vertically forcing piles, well conductors, soil sampling devices, and other objects into subsea soil. Existing hammering devices are very large, very expensive to deploy, and because of their size and complexity, existing hammering devices tend to be limited to relatively shallow seawater depths and to driving relatively large objects. Current technology also includes drilling a hole and/or jetting a hole into the ocean floor, then inserting an object into the hole, but these techniques require a very large, expensive ship or platform and a considerable amount of time for installing the object. Also, in the case of piles, well conductors and other objects that are to remain in the soil, the objects need to be longer than would be necessary if the objects were instead driven into the subsea soil. This is due to the reduced holding capacity or strength of an object that is placed in a drilled or jetted hole, because of the soil disturbance at the walls of the hole and also the enlarged size of the hole relative to the object.
U.S. Pat. No. 5,662,175, issued to Warrington et al. and incorporated by reference, describes a pile hammer that can be used under water, which uses water as a hydraulic fluid. A hydraulic power pack is located at the surface and connected by hoses to a hydraulically-operated ram. There is a practical limit to the depth at which the pile hammer can be used because it is impractical to pump water through hoses to a great depth.
U.S. Pat. Nos. 4,872,514; 5,667,341; 5,788,418; and 5,915,883, issued to Kuehn and incorporated by reference, describe, in general, pile drivers that can be used in relatively deep water. Kuehn's '883 patent describes a submersible hydraulic driving unit that can be connected to the driving mechanism of an underwater ramming apparatus or cut-off tool. The driving unit has a hydraulic pump powered by an electric motor, which receives electricity from the surface through an umbilical cable. The driving unit has another umbilical cable that plugs into the ramming apparatus or cut-off tool, and a remotely-operated vehicle (ROV) is used to observe and make that connection. In the process of lowering equipment supported by an umbilical cable, the umbilical cable is prone to damage, and Kuehn's '341 patent describes using the umbilical cable of an ROV for signal and data transmission with a driving unit.
International Patent Application No. PCT/GB2006/001239, bearing International Publication No. WO2006109018, invented by Clive Jones and incorporated by reference for all purposes, describes an apparatus for driving a pile into an underwater seabed, which includes a pile guide that includes a base frame, a guide member mounted on the base frame and configured to guide a pile, a device for driving the pile into the seabed, and a power supply for supplying power to drive the device. The Jones application describes a power supply that is part of a remotely operated vehicle (ROV). Jones discloses that hydraulic hammers such as the IHC Hydrohammers supplied by Dutch Company IHC Hydrohammer BV can be used as the pile driving device. According to an IHC brochure, the IHC Hydrohammer includes a hammer and a piston rod constructed as a single piece and an enclosure for the hammer, which indicates that the assembly is designed so that the hammer reciprocates in an essentially clean, dry, gaseous environment, which is an environment that is difficult to maintain while under the pressure imparted by very deep water.